The field of the invention is that of lubrication systems for internal combustion engines. More specifically, the field is that of phase timed lubrication systems for a crankshaft counterbalancing system.
In single cylinder horizontal or vertical air cooled engines, bearings are lubricated using a pressurized gallery system. The connecting rod is lubricated from the cylinder block bearing via a cross drilled oil passage within the crankshaft. The passage is drilled at a diagonal from the cylinder block crank main journal through the upper crank cheek and through the crank pin to provide a lubrication passage to the rod journal. The lubricant feed to the crank pin pressurizes the crank pin, and excess lubricant thrown off the rod bearing also lubricates the piston cylinder bore with the throw off of the excess oil from the rod journal. This system works for a completely pressurized bearing journal system and provides adequate lubrication for the internal parts of an engine.
Dealing with smaller engines, their crankshafts have a more limited space within the rotational plane of the crankcase, which limits the size and mass of the crankshaft counterweights. Counterweight designs have changed to accommodate smaller engines; rather than increase the mass of the counterweight, the mass of the opposing pin is reduced by drilling a balance hole through the center of the crank pin and crankshaft webs. However, the oil feed passage to the journal surface of the crank pin is interrupted by the cross drilled balance hole.
A lubrication system which presents one solution to the oil passage interruption problem is described in U.S. Pat. No. 4,768,397 (Adams). Adams describes using a tubular lubricant conduit to bridge the balance hole and re-establish the lubricant path. Yet, this system requires an additional operation in its manufacture, along with the additional tube component. Further, the tubular conduit is a source of potential problems due to the tube not being retained and migrating due to centrifugal force, which would interrupt the lubricant flow and cause the connecting rod bearing to score and fail.
Other methods use splash or general pressure spray lubrication within the crankcase to lubricate the connecting rod bearing and cylinder bore, but these methods are not as positive as pressure lubrication in the connecting rod bearing and bore area. For example, a gallery system used for lubricating the main shaft of an engine can have a cross-drilled aperture in the lubricant passage which allows oil to spray out continuously. The continuous spray sporadically lubricates the rod bearing, with the oil emitting from the upper portion of the cylinder in a direction generally perpendicular to the bearing's plane of rotation so that oil reaching the bearing is not guaranteed.
A spray system is described in U.S. Pat. No. 2,678,702 (O'Harrow). The lubrication system of O'Harrow has a camshaft with an axially located passage and a series of lateral passages. The axially located passage serves as a conduit for lubricating oil, while the lateral passages continuously spray lubricant oil. Connecting rods have apertures which allow oil to penetrate to journal positions. A recess is placed within each journal for containing sprayed oil. The aperture and spray are designed to be aligned at the point when the centrifugal force of maximum intensity between the shaft axis and the bearing axis is coincident with the centrifugal force at the journal surface within the recess. However, this point of coincidence is at the point of rotation where the journal is at its farthest point from the oil spray, so that less of the spray actually reaches the journal because of scatter. Also, the spray system of O'Harrow requires a significant amount of space within the crankcase which is not present in smaller engines. Further, the O'Harrow spray system does not account for the camshaft and the crankshaft rotating at different speeds.
Thus, an improved spray lubrication system for internal combustion engines is needed. Also needed is a system which effectively delivers sufficient amounts of oil both efficiently and economically. A further need exists for such a lubrication system which does not require additional components. Still another need involves an efficient lubrication system for shafts with different rotational speeds.